Motor/Transmission combo suggestions for a '65 C20
 

My goal is a highway cruiser that I can take on trips and do 75 comfortably and safely without earplugs :) My '65 C20 has a 283/4-speed combo. I have owned a few trucks with the inline 292 and I am leaning toward that. Thinking a rebuilt 292 with an auto transmission. Suggestions for the type of transmission? Also, if i wanted a column shift would there be anything that would look period correct? Ideas? Thanks guys!

Re: Motor/Transmission combo suggestions for a '65 C20
 

My personal approach would be to keep (and rebuild if required) the 283 and add an overdrive trans. If you want to stick (pun intended) with a manual, I’d consider a T5 or NV3500/4500 swap. If you want to switch to an automatic (it’s purely a personal choice you need to make) then a 700R4 or 2004R will meet your goals. There’s really no reason to swap to a 292 to achieve your goal of highway driving and that swap will add unnecessary cost - and if that 283 is original to the truck, even more reason to keep it. Again, just my 2 cents. What is your rear end gearing? A C20 can have pretty steep gears, so in order to manage expectations - it would be good to understand “how much” that overdrive trans will help before you dive in head first. If you tell us your rear tire diameter and rear gearing, I can give you a much more detailed answer. Btw, HERE is how I did the T5 swap in my 66. I believe there are more spacer plate options on the market these days, you shouldn't have to make your own like i did in the thread. Another option would be to leave everything as is (rebuild anything that needs it) and add in a Gear Vendors over/underdrive unit. Instant overdrive for your 4-speed (and gear-splitter capability). Can be pricey, but not much more than a T5 swap in the end. If you still plan to use your truck for any heavy hauling, trailering (or burnouts), I'd avoid the T5, not stout enough for prolonged HD use. But if just gonna highway cruise, it would be fine.

Re: Motor/Transmission combo suggestions for a '65 C20
 

Thanks for your input jocko. It is the original 283 and though I have done quite a bit of wrenching in my time I have never rebuilt a motor. Maybe it's time to do it though. I am going Automatic so the 700r might be my go to. I guess i just like the 292 because it is something different but i know small block parts are a lot easier to come by and I'm hesitant to switch out the 283, I'm not to familiar with the rear end gearing. How would I tell what gearing I currently have?

Re: Motor/Transmission combo suggestions for a '65 C20
 

There is a 2 letter stamp on top or rear of the drivers side axle tube, such as HE or HF or HG or HH etc. it will tell you what came in the truck originally if:
a. It was an original rear end
b. Someone hasn't changed it before you bought it.
The codes are listed here in these two pages posted for the 65:
1. https://public.dm.files.1drv.com/y4p...drts=329082205
2. https://public.dm.files.1drv.com/y4p...drts=329082205

Re: Motor/Transmission combo suggestions for a '65 C20
 

Thank you Rocknrod!

Re: Motor/Transmission combo suggestions for a '65 C20
 

As an example (on a 64 C10):

Re: Motor/Transmission combo suggestions for a '65 C20
 

If you don't see any codes on the axle or at least want to confirm in case gearing may have been swapped out, you can:

a) if you have a tach in the truck and a GPS (for speed reading, don't use speedo) and measure actual tire diameter - we can calculate it with a highway speed hack of GPS speed vs RPM.
b) count teeth on ring & pinion (or look for a stamp on the gearset that shows pinion to gear ratio, something like 45-11 (i.e. 45 on ring and 11 on pinion=4.10, example only)).
c) as a last resort (since it's not the most accurate method out there) do the old jack it up and count d/s revs per tire rev method, not always accurate but you can get close
First, you need to know if you have a posi - if unsure, jack up both rear wheels, then ensure parking brake is off and trans in neutral, rotate one tire by hand. If the other tire rotates the same direction (i.e. as they would when rolling down the street), that indicates you likely have a posi. If the tires rotate in opposite directions, you likely have an open diff.

If posi diff - leave both wheels jacked up and count how many revs of the d/s occur in 1 full tire rotation. (chalk mark on d/s and tire outer dia help to visualize)
If open diff - lower one side to keep one tire in contact with the ground so it won't rotate, then count how many revs of the d/s occur in 2 full rotations of the raised tire.

The # of d/s rotations counted in the above two scenarios is approximately your gear ratio.
If you know your rear is stock, then you can compare your results to what was available for your truck - i.e. 4.11 or 4.57, otherwise. If originality is unknown, then at least you can get close to what it could be.

Re: Motor/Transmission combo suggestions for a '65 C20
 

I built my ‘65 C10 with the goal of comfortable highway cruising. I ended up going with a TBI 350 / 700R4 combo with 3.08 rear gears. This setup turns about 2200rpm at 75mph with the converter locked. I am running the full fuel injection system so it always starts regardless of the temp and has been reliable. I am planning to long haul Power Tour this summer in the truck. Wind noise is still a challenge with these trucks so definitely recommend insulating the firewall, floors etc. and replacing all of the seals and window felts.

Re: Motor/Transmission combo suggestions for a '65 C20
 

Price of fuel these days!!!!

Re: Motor/Transmission combo suggestions for a '65 C20
 

I agree on the gear vendors OD, it seems to be the simplest. Going thru searches on the subject, its amazing how difficult it is to find a 2WD '65-'66 3/4 ton with SM 420 4spd. gear vendors install build. It seems like the choice with the least amount of major modifications ( drive shaft shortening). 99% sure this C 20 has a 4.56 rear, so if overdrive is .73 (not sure, getting conflicting info ) .73x4.56=3.32 or possible .78 overdrive .78x4.56=3.55 IMO a .78 overdrive is better for a pickup than .73

Re: Motor/Transmission combo suggestions for a '65 C20
 

"Estimate total price starting at $50,000"
Gas is cheaper.

Re: Motor/Transmission combo suggestions for a '65 C20
 

I also feel the GV o/u is the way to go in this scenario (if it were me, because I like to keep as much original equipment on the truck as possible, just a preference - and it's reversible). If the truck does have the 4.57, your math illustrates how an overdrive can only "help" the situation, not necessarily solve it, when there's that much gearing to overcome. I had a 57 chev in high school with a muncie 4-speed and 3.55 gears - and it still turned relatively high rpm at highway speeds - but yes would still be a HUGE improvement over a 4.57. If this truck happens to have 4.11/4.10, the GV unit puts highway RPM right in the sweet spot. The more I think about it, if it were my truck, I'd probably still want to preserve its HD nature/capability - and T5 (and even a 700R4, unless "built") aren't quite as sturdy as that original SM420. As GV o/u's are pretty indestructible, it's a great option to greatly improve drivability without sacrificing anything (except a few extra $).

Re: Motor/Transmission combo suggestions for a '65 C20
 

My bad, 4.57 is the correct Eaton Ho52 ratio, thanks Jocko. From my observations, most are 4.57, even though 4.11 was an optional ratio. I mentioned '65-'66 C 20 because they don't have the parking brake drum that is found on back of the trans of '60-'64's 4 spd C 20's.

Re: Motor/Transmission combo suggestions for a '65 C20
 

While the 292 is my favorite truck engine, if I was looking for a Hi-Way cruiser, I would stick with the 283. The long stroke of the 292 that gives it that great low end grunt really doesn't like to be wound out. Back in the early 80's I put a rod through the block on a 1 ton 292 company truck by going way too fast on the freeway. They installed a rebuilt 283 out of another old Chevy they had and boy was that a lot smoother at high speeds.
If you can find a 4:10 pumpkin out of a later HO rear end that's the cheapest and easiest way to get more speed. Did that on mine and am very happy with the results.
As far as the tranny goes, I like the combo of the 4:10's for the road, but still having the granny gear when you need to use it as a truck. Plus, both that trans and rear are pretty much impossible to break.
I've always wanted to put a GV behind an SM420. being able to have OD and split those gears would be the ultimate transmission IMO. Ironically I have the father of the GV in my Triumph TR4. It's based on the old Laycock OD units that went into many British cars of the 50's and 60's. Great fun to split the gears in those cars with the flick of a switch, and no clutch required!
Good luck whatever you decide to do
Tom

Re: Motor/Transmission combo suggestions for a '65 C20
 

If you’re looking to build a truck with dependability and highway cruising of course it won’t looks stock but you can’t beat an LS Drive train with 373 gears drove my 65 across country towing a small camper at highway speed couldn’t imagine doing it with a 283 and the 283 has always been my favorite small block have Owned a ton of them

Re: Motor/Transmission combo suggestions for a '65 C20
 

I agree, however, everything comes with a price. Any ball park figure on complete cost including every part and modification necessary for the conversion. Assuming your truck originally was a V8 3 speed.

Re: Motor/Transmission combo suggestions for a '65 C20
 

You might want to check rebuild costs on your 283, you may be surprised, can most likely do a 350 cheaper….more parts availability…make sense, no, but what does these days

Re: Motor/Transmission combo suggestions for a '65 C20
 

5 k that includes trans

Re: Motor/Transmission combo suggestions for a '65 C20
 

Where is that?

Re: Motor/Transmission combo suggestions for a '65 C20
 

Yes, I am curious on that also…:gmc2:

Re: Motor/Transmission combo suggestions for a '65 C20
 

I picked this mother up about six years ago when I started The build it came from a Pontiac G8 an LS two with a sixL 80 E transmission 60 k miles $3500 shipped to my door from an outfit out of New York that primarily specialize in Corvettes The rest of the money was spent on having the ECM Flashed bye a place in So Florida Don’t remember their name right now A pair of electric fans and some other miscellaneous stuff like motor mounts, driveshaft I did End up buying a harness so really probably closer to 5500